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Judging by the box office receipts, legions of people have been lining up to see Avatar. What those numbers don't tell is how many people walked out after 15 minutes because the 3D effects made them sick. If this story is to be believed, it could be a lot.

Creating the illusion of 3D involves messing a little bit with the body's vestibular system, the organs that connect the ear to the brain and give us a sense of balance. About 35 to 40 percent of the population suffers from some kind of vestibular problem, according to the Vestibular Disorders Association. Such problems can lead to "sensory conflict" when watching 3D, which affects the vestibular system in a way similar to being poisoned. The body reacts by becoming nauseated, trying to expel the poison.

It's doubtful that 40 percent of Avatar attendees walked out because they felt sick, but Googling "Avatar nausea" turns up tons of anecdotal stories. Since Avatar has got Hollywood hot for 3D, the future of moviegoing is looking uncertain for a significant chunk of the audience. People who react badly to 3D may need to be segregated to 2D theaters while their significant others enjoy Clash of the Titans or Harry Potter in 3D. That, or we all get used to theater floors being a lot messier.

The best solution might be a 3D technology that looks fine in 2D if you're not wearing glasses. Or maybe glasses that don't create the 3D effect, just a regular 2D image — assuming that didn't create vestibular issues as well. Glasses-free 3D might work, too.

What should be done about people who react badly to 3D? Share your stories in the comments.